Influence of preparation methods on structure and properties of PA6/PA66 blends: A comparison of melt‐mixing and in situ blending

Abstract

The blends composed of polyamide 6 (PA6) and polyamide 66 (PA66) were obtained using two different preparation methods, one of which was the melt-mixing through a twin-screw extruder and the subsequent injection molding; and the other, the in situ blending through anionic polymerization of e-caprolactam in the presence of PA66. For the former, there existed a remarkable improvement in toughness but a drastic drop in strength and modulus; however, for the latter, a reverse but less significant trend of mechanical properties change appeared. Various characterizations were conducted, including the analyses of crystalline morphology, crystallographic form, and crystallization and melting behaviors using polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC), respectively; observation of morphology of fractured surface with scanning electron microscope (SEM); measurement of glass transition through dynamic mechanical analysis (DMA); and the intermolecular interaction as well as the interchange reaction between the two components by Fourier transform infrared spectrometry (FT-IR) and 13 C solution NMR. The presence and absence of interchange reaction was verified for the in situ and melt-mixed blends, respectively. It is believed that the transreaction resulted in a drop in glass transition temperature (T g ) for the in situ blends, contrary to an increase of T g with increasing PA66 content for the melt-mixed ones. And the two kinds of fabrication methods led to significant differences in the crystallographic form, spherulite size and crystalline content and perfection as well. Accordingly, it is attempted to explain the reasons for the opposite trends of changes in the mechanical properties for these two blends.

Crystallization of polyamide 56/polyamide 66 blends: Non‐isothermal crystallization kinetics

“…PA66 has a relatively high crystallization rate which can be used as a nucleating agent to promote the crystallization of PET . Blending different kinds of polyamide is also a good method to improve some properties . For example, the crystallinity of PA6 can be efficiently reduced by blending with PA66 .…”

Multilevel‐layer‐structured polyamide 6/poly(trimethylene terephthalate) nanofibrous membranes for low‐pressure air filtration

“…The diameter of PA6 nanofibers is thinner than that of other polymer fibers, which have been examined in previous research. In previous studies, multilevel-layer-structured membranes of PA6 were fabricated with polyamide 66, 34,35 poly(ethylene terephthalate), 36 multiwalled nanotubes, 37 polyurethane, 38 poly(vinylidene fluoride), 39 poly(vinyl acetate), 40 and so forth. [30][31][32] As the time of spinning continued, pure PA6 nanofiber membranes obtained a high efficiency and excessive resistance.…”

“…33 Consequently, obtaining a PA6 membrane with a high efficiency and low drop pressure was the main purpose in this study. In previous studies, multilevel-layer-structured membranes of PA6 were fabricated with polyamide 66, 34,35 poly(ethylene terephthalate), 36 multiwalled nanotubes, 37 polyurethane, 38 poly(vinylidene fluoride), 39 poly(vinyl acetate), 40 and so forth. PA6 and poly(trimethylene terephthalate) (PTT) composite membranes have rarely been studied.…”

Reciclagem de rejeitos de poli(tereftalato de etileno) (PET) e de poliamida (PA) por meio de extrusão reativa para a preparação de blendas

“…Os resultados de DSC evidenciam a ocorrência de interação entre os componentes PET e PA que pode ser do tipo intermolecular ou estar relacionada à formação de copolímeros devido às possíveis trans-reações entre o PET e a PA. Os copolímeros formados apresentam segmentos dos dois polímeros da blenda e cada segmento tem maior afinidade química pela fase rica no polímero correspondente, promovendo maior interação interfacial e consequente compatibilização do sistema. Alguns catalisadores como os do tipo organo-estanho podem aumentar o rendimento de formação de copolímeros, melhorando a compatilidade da blenda [6,7] .…”

“…Da mesma forma que ocorre em presença de umidade, as trocas de grupos químicos durante o processamento em altas temperaturas pode ocorrer com grupos do outro polímero de condensação que compõe a blenda polimérica [6,7] . As trans-reações, como são chamadas as reações de trocas de segmentos de cadeia em polímeros de condensação, podem ocorrer entre dois poliésteres (transesterificação), duas poliamidas (transaminação) e também entre um poliéster e uma poliamida [6,7] .Os rejeitos de pneus usados representam outra classe de material polimérico com potencial poluidor elevado. O elastômero, principal constituinte dos pneus, encontra-se na forma reticulada, o que dificulta a sua reciclagem por métodos termo-mecânicos.…”